1. Field of the Invention
The present invention relates to microgels, coating compositions having the microgels, methods of coating substrates with the coating compositions, and substrates coated with the coating compositions.
2. Description of Related Art
Industrial coatings are surface protective coatings applied to substrates and are typically cured or crosslinked to form continuous films for decorative and protective purposes. Protective coatings ordinarily comprise an organic polymeric binder, pigments and various additives, where the polymeric binder acts as a fluid vehicle for the pigments and imparts rheological properties to the coating. Upon curing or crosslinking, the polymeric binder hardens and functions as a binder for the pigments and provides adhesion of the dried film to the substrate.
Epoxy resins have been particularly desirable for use in protective coatings as a polymeric binder. The epoxy resins advantageously provide toughness, flexibility, adhesion and chemical resistance to the resulting coating compositions. Water-dispersed coating compositions containing epoxy resins are highly desirable as packaging coating compositions for food and beverage substrates, and are particularly useful for the interior surfaces of such substrates.
Commonly-owned U.S. Pat. No. 5,508,325 describes coating compositions having microgels prepared by crosslinking a carboxyl-functional polymer with an epoxy resin. Commonly-owned U.S. Pat. Nos. 5,733,239 and 5,877,239 also relate to microgel technology. The entire contents of these three patents are incorporated herein by reference.